chrystler town &country reads po172....no maf sensor...how

Resolved Question:

Hello and thanks for your question. My name is XXXXX XXXXX I will do all I can to help.

Edward :

Let me first ask, Do you have the 3.3 v6 engine in this van?

Customer:

yes

Edward :

alright, Give me just a second to get this answer for you. thank you.

Edward :

say a second, I mean a few minutes. !! :)

Edward :

Do you have any stalling sometimes or trouble starting the engine by chance?

Edward :

I know you said it runs badly, but I'm looking for stalling at idle, or no start. Have you experienced that ?

Customer:

no trouble starting but it wants to stall...Saturday I read the codes and cylinders 4 and 5 were misfiring as well as po172...changed plugs and wires and still runs horrible.

Edward :

alright, is it puffing black smoke? and flooding? you smell gas?

Customer:

no

Edward :

alright, Did the P0172 come back after replacing the plugs and wires? check engien light came back on pretty quick?

Customer:

right away..

Edward :

alright. and that is the only code it sets right away?

Customer:

yes sir...

Edward :

No MAP sensor codes with it?

Edward :

Sorry so many questions, trying to make sure I have as much info as I can get.

Customer:

no..originally there were 4 codes...the three I told you and the last one was multiple misfires.

Edward :

OK I understand.

Edward :

One thing we need to check, is the fuel pressure when you shut the engine off. Fuel pressure should hold steady around 35-45 psi when you cut the key off. If the pressure leaks down fast after the engine is cut off, That could signal a stuck injector. Check the fuel pressure running too, should be around 50-55 psi.

Edward :

Do you have a fuel pressure gauge by chance?

Customer:

not here....its at my dads 45 mins. away

Edward :

ok,

Edward :

well that is the first thing I would check, make sure fuel pressure is right, (if it's too high would give you that P0172 rich code as well).

Edward :

or if a injector is hung open, it will fall quickly when key is turned off.

Edward :

Then you have to pull up the fuel rail, put some cardboard under the injectors and see which one is leaking.

Edward :

That is one theory.

Edward :

The other thing, Did you check each the plug wires on cyl. 4 and 5, and make sure the coil pack was putting spark out to these cylinders? I know you said you replaced plugs and wires, is cyl. 4 and 5 wire firing a spark tester?

Edward :

I wanna make sure the cylinders are getting spark.

Customer:

yes I do have spark at # XXXXX & 5. didn't check before I replaced them

Edward :

OK, If the coil is putting spark out on 4 and 5, then we can assume the plugs are firing if the wires and plugs are new.

Customer:

it idles rough and when I step on gas pedal it spits and sputters...gets better at higher rpms

Edward :

Alright, We want to be sure compression on those cylinders is good too.

Edward :

I've seen broken or weak valve springs cause it on 3.3 before.

Edward :

You haven't had to add any coolant and no overheating ?

Customer:

nope

Edward :

OK, Headgasket is prob. ok then.

Edward :

What code was stored first when you initally checked them? misfires or the P0172?

Customer:

p0172

Edward :

OK, so we could assume that the rich running condition caused the misfire codes and not the other way around if the P0172 was stored first and came back.

Customer:

plugs 4 &5 were carboned up pretty good

Edward :

Alright, when this happens, the engine is getting access fuel from somewhere.

Edward :

Check the pressure, make sure it's around 50 psi running, then it holds pressure when key off.

Edward :

Check your carbon canister as well. If it's saturated with fuel. that can cause it.

Customer:

ok....that gives me some direction

Edward :

If fuel pressure is good in the running and non running test, I would suspect a fuel soaked carbon canister, or possibly a failing MAP sensor.

Edward :

One more thing to try, is block off the EGR valve vacuum, and see if that makes any difference. If the EGR valve is getting vacuum all the time, solenoid could be stuck.

Edward :

so I would pull the vacuum line, block the line, go drive it and see if you got the p0172 back.

Edward :

I believe you'll find your problem in one of those three things. Tricky to exact pin point it from my end. But I believe it's one of those 3 scenarios.

I will tell you that...the things you have to go through to be an Expert are quite rigorous.

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